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Have read several threads about the 650 M sport exhaust, and listened to some clips.(Southern for one) Just wondering if anybody has actually determined if there is a design difference between the systems in the sport vs non sport

There is a huge difference. When I built my car, I was under the impression that there was no difference, but I got the M Sport Package anyway because of the aesthetic changes. I got really lucky. I've driven several non-M Sport convertibles, and the exhaust is very tame. I spent several hours in these cars between my test drive and my PCD, and both times I left with a feeling of either apathy or disappointment regarding the noise. I was pretty disappointed in the sound when I took my test drive, but I figured it was just BMW's way of saying this car is geared toward an older, more mature buyer who prefers a comfortable, quite, luxurious coupe. The non-M Sport cars definitely meet these criteria. Add the M Sport, and you still have the same features I just mentioned, but the car is slightly louder in Comfort compared to the non-M cars and a lot louder when you are in Sport. The first time I ever heard an M Sport 650i start from cold was at the dealership right after they released the coupe (and M Sport Package - which wasn't available at the convertible's launch), and there was a "Holy $h!t" look on my face as well as the two CAs standing behind the car when I started the engine. I often use Comfort mode as a "mute button" when I see cops or when I'm driving through a part of town where I prefer to be inconspicuous.

Exhaust noise is subjective, so describing its level of loudness is hard to adequately convey without first hand experience. I've never been an exhaust buff, and I didn't know how much I wanted this M-tuned exhaust until I had it. I would have been content with the non-M if I could live ignorant of the M Sport's superior sound, but I think it would have just about killed me if I heard an M Sport 6er after buying the non-M Sport version. I wouldn't give up my exhaust for anything. For a $100k coupe, I think a decent poo shoot noise is expected, and that is why I was disappointed by the non-M. Don't get me wrong, I think the non-M car is beautiful, and its exhaust is probably loud enough for some people, but I was cross-shopping with the XKR, 911, CLS 63, and C 63 - four relatively sporty cars, and it's hard to beat the sound coming from an AMG's car without paying Aston/Ferrari money.

I know none of the BMW NA press materials, specs, etc. discuss the exhaust upgrade - something you'd think they'd make a point to advertise - but it's definitely one of those things where you'll believe it when you see it... or hear it . Thom also confirmed with a BMW rep a few months back that there are different parts and item numbers for the M Sport vs. the regular 650i.

Thanks for all the details. All I have driven up to this point is 2 non -sport 650's. My dealer e-mailed me yesterday that he has a Tanzanite blue M sport 650 coming in next couple weeks. I will finally get a chance to check out the difference. I also did not realize there was a difference in exhaust sound/volume based on the comfort/sport settings. And it is very interesting that BMW does not mention this anywhere.

Thanks for all the details. All I have driven up to this point is 2 non -sport 650's. My dealer e-mailed me yesterday that he has a Tanzanite blue M sport 650 coming in next couple weeks. I will finally get a chance to check out the difference. I also did not realize there was a difference in exhaust sound/volume based on the comfort/sport settings. And it is very interesting that BMW does not mention this anywhere.

Yep. Sport mode turns the car into a car deserving of the 650i badge. Comfort is fine, but I pretty much only use it in three situations:
1. Shut the car up when I don't want to draw attention to myself.
2. Trying to keep the tach in the lower RPMs - break-in period, stretch a tank of gas, warning light comes on and I want to keep the stress on the engine to a minumum.
3. Driving others around - specifically, others who couldn't care less about the car so the importance of comfort >> sportiness.

I fall in the "older" category that wants a little more peace and quiet in my life, especially after owning an M3. The M3 had a single mode exhaust and was always on edge. I use Comfort mode a lot more than some, during my work commute, etc. It's so easy to flip to sport when necessary, so I see no point in keeping it there (just my way). I must point out however, that the non-M Sport also has a dual mode exhaust, and while quieter in both modes than the M Sport, it also gets louder in the sport modes, especially under load. It also switches to "loud" in park during a cold start.

I don't notice much of a difference between Sport and Comfort on the M-Sport exhaust. If there is a difference, it is subtle. Southern's may be different, but I can't exactly "mute" mine. It sounds good through all the drive modes but never would I describe it as being "loud." Especially not enough to draw attention to myself. Then again, I live in a place where there are a lot of modified cars with loud exhausts. I guess it's all relative.

There is, however, a huge difference between the M-Sport and non M-Sport exhaust. That is not even a question. I've owned both variants for months.

Then again, I live in a place where there are a lot of modified cars with loud exhausts. I guess it's all relative.

Just go ahead and say it - I live in a backwards a$$ part of the country in my own little delusional world haha

I know what you mean though. As I said above, "loud" is a subjective term. While I do think it does draw some attention to me, I wouldn't consider it "loud" like a 1995 Honda Civic with an aftermarket exhaust... or "loud" like an Aston's V12, but I have a lot more experience hearing the former than the latter .

i don't notice much of a difference between sport and comfort on the m-sport exhaust. If there is a difference, it is subtle. Southern's may be different, but i can't exactly "mute" mine. It sounds good through all the drive modes but never would i describe it as being "loud." especially not enough to draw attention to myself. Then again, i live in a place where there are a lot of modified cars with loud exhausts. I guess it's all relative.

There is, however, a huge difference between the m-sport and non m-sport exhaust. That is not even a question. I've owned both variants for months.

+1

If you are deciding between the two, as long as you don't really want Vermillion Red, go for the M-Sport. There really is a huge difference and just too much to list.